When Moisture Attacks and the Impact to Your Building Envelope

In September 2017, two category 4 hurricanes
and one category 5 hurricane devastated Florida, Texas, Puerto Rico,
the U.S. Virgin Islands and more with a total
cost of up to $475 billion in damages. During the 2016-2017
rainy season, SF Gate reported that
California received more rain in just a few months than the state
had seen in the previous five years – combined. And, according to
The Weather Channel, by January 2017, Bismarck, North Dakota had
already received 31 inches of snow above average, and had exceeded
the entire average season’s worth of snow. It’s hard to deny that
we’ve been seeing more volatile moisture events, and it begs the
question as to whether they are the new normal.

Not surprisingly, the significant amounts of
precipitation that come with these extreme weather events has
obvious catastrophic and in some cases, even irreparable, effects to
buildings in which we live, work and play. But what about the damage
the inconspicuous moisture that accumulates inside these buildings
as a result of these events (as well as ventilation issues, poor
insulation, air leaks and more) can cause ongoing, not only to the
structure itself, but also to our health?

Thanks to common problems with moisture
control, simply breathing indoors can harm us. There is a strong
association between exposure to damp indoor environments and adverse
health effects, according to
the Institute of Medicine (IOM) of the National Academy of Sciences.
It’s terrible to think that moisture might be lurking in the
background unnoticed while being detrimental to the health of a
building’s occupants over time. This hurts our pocket books, too –
moisture-related health problems and building damage can be
extremely expensive. Berkeley Lab estimates that
the annual asthma-related medical costs attributable to exposures to
dampness and mold total approximately $3.5 billion in the U.S, so
cutting back on moisture issues could help reduce costs from having
to visit the doctor.

In many ways, moisture control is one of the
unsung heroes of any building. The truth is, it’s fundamental to the
proper functioning of any building. In addition to protecting
occupants from adverse health effects, controlling moisture also
protects the building and its mechanical systems and its contents
from physical or chemical damage. Yet, moisture issues are common.

A little bit of water makes for big problems Moisture-related problems are common in U.S. buildings.
Between 1994 and 1998, the U.S. Environmental Protection Agency
(EPA) Building Assessment Survey and Evaluation (BASE) study collected
information about the indoor air quality of 100 randomly selected
public and private office buildings in the 10 U.S. climatic regions.
The BASE study found that 85 percent of the buildings had been
damaged by water at some time, and 45 percent had leaks at the time
of data collection. A 2007
study in ASHRAE journal found that, out of 17,000 construction
defect claims, 69 percent were the result of moisture-related
defects in building enclosure systems.

Moisture-related issues such as damp and
moldy indoor environments can lead to increased cases of upper
respiratory problems, including coughing, wheezing and asthma
aggravation, among others, according to the EPA. There’s also
evidence that high levels of building moisture can lead to dyspnea
(shortness of breath), lower respiratory illness and asthma development.

As a result of such high levels of damage,
moisture-related problems are also costly – American businesses can
spend as much as $9 billion annually repairing and litigating
damages from moisture intrusion.

Managing moisture through better design For commercial and residential buildings alike, one of the
best ways to address moisture-related problems is to attempt to
prevent them from happening in the first place. Designing building
enclosures to reduce water intrusion is the best place to start.
Then it’s important to look at water condensation – make sure
exterior enclosures are airtight by using continuous air barrier
systems around the entire enclosure. To be effective, these
systems must reduce air leakage into the exterior enclosure
assemblies during cold weather, and leakage of outdoor air into the
exterior enclosure or interior wall, ceiling, and floor cavities
during warm weather. Air sealing an enclosure makes it easier to
manage indoor-outdoor air pressure relationships with practical
airflow rates.

Meeting minimum R-values in accordance with
the International
Energy Codewill help ensure the building is up to standards.
Meanwhile, managing the flow of heat and water vapor through all
enclosure assemblies can help avoid condensation on materials
inboard of the drainage plane. Insulating materials must also be
used to manage heat flow to keep the surface temperature of low
permeability materials inside the enclosure above the expected dew
point. A continuous thermal barrier also is necessary to reduce
condensation on the interior surfaces of exterior walls and ceilings
during heating conditions. The insulation layer must be continuous
to reduce condensation due to thermal shorts. Areas of high concern
include metal framing, concrete slab edges and angle iron ledgers.

Focusing on foundations and walls Foundations and walls are vulnerable to moisture problems.
During warm weather, water may condense on foundation materials
because the materials are cooler than the outdoor air. Likewise,
crawl spaces and basements have more extensive contact with cool
damp or wet soil than slab-on-grade foundations. That’s why many
moisture problems can be avoided by properly designing the
foundation. This can be done by specifying insulating materials for
the outside of foundation walls that can tolerate exposure to the
earth. Extruded polystyrene (XPS),high-density expanded polystyrene
(EPS) foam boards, or closed-cell spray polyurethane foam (SPF)
insulation can be successfully used to insulate outside surfaces of
foundation walls. Given wet materials don’t maintain the same
R-values it’s essential to understand that using water-resistant
materials plays a major role in the performance of a building’
design. Water absorption is commonly measured for these types of
materials through standardized testing, such as ASTM C272.

Moisture control is an important aspect of
designing an integrated building enclosure. Failing to properly
design walls to manage moisture, as well as failing to transition
walls with other building enclosure components – such as the roof
and foundation – can lead to serious moisture-related damage. To fix
these damages, multiple building components may need to be replaced,
which is not only extremely difficult to accomplish due to the
façade making components inaccessible, but costs a pretty penny in
high repair fees, too.

Designing exterior walls to manage excessive
rainwater will help mitigate this and is a great start. Monolithic,
conforming materials such as a liquid flashing solution to seal
around common problem areas like windows, doors, outdoor intakes,
exhaust, ducts and other penetrations, can help achieve the water
tight barrier your building needs. Exterior walls must also reduce
condensation. Cool surfaces within the building envelope can lead to
water vapor condensing. Avoiding this condensation can be attempted
by controlling the temperature with continuous insulation.

It’s important to understand these issues
clearly. Moisture-related issues – which is an even larger concern
if recent weather events are any indication – impact the health of
building occupants and can be mitigated with a design that minimizes
water intrusion. Beyond damages from weather, we see from multiple
studies that buildings often unknowingly have leaks and need to be
repaired immediately to minimize further issues and higher costs due
to repairs. It’s also necessary to pay attention to the foundation
and use a design that minimizes condensation from wreaking havoc on
crawl spaces, basements and walls.

Staring in the eye of a natural disaster
serves as a reminder that buildings need to be designed with the
impacts of moisture in mind. Designing a more resilient building
will not only help to prepare for unforeseen issues, but will help
the building to continue to thrive over time.